ARC Packages And Modules Available

Several packages and libraries implementing ARC are now available, and are linked from our new Resources page. Mailbox providers and maintainers of mailing list manager (MLM) software can use these components to start adding ARC functionality to their products and services today.

For those creating their own ARC modules and products, the new ARC test suite from ValiMail is an ideal validation tool – and completely free to use. The test suite has been used to validate the dkimpy package with an Python library and command line tools, and the OpenARC milter is currently being validated.

Or if you just want a turnkey solution, add ARC to your platform by using the fully supported MailerQ commercial MTA from Copernica.

Patches to add ARC functions to the Mailman MLM should be available soon, and ARC should be integrated into the Sympa MLM by mid-year.


Introduction to ARC to be presented at M3AAWG 38 in Paris on Oct 26

ARC-logo-150x150Kurt Andersen (LinkedIn) and Steve Jones ( will be presenting an overview of the Authenticated Received Chain (ARC) protocol at the 38th Messaging, Malware, and Mobile Anti-Abuse Working Group (M3AAWG) meeting in Paris, France from 1-2PM local time on Wednesday, October 26th. The description of this session from the conference agenda reads:

The new ARC specification holds the potential of addressing a number of the problems with DKIM signature breakage that cause problems for DMARC authentication. If you are interested in this topic, please join some of the key contributors to the spec for an introduction and Q&A regarding the proposed standard.

Much of the background information that will be presented in this session is available here, for those who cannot attend the session.


Two ARC Implementations Tested At Interoperability Event

On February 19th representatives from AOL (NYSE:VZ)  and Google (NASDAQ:GOOG) successfully tested the first two implementations of the ARC protocol at an interoperability event. LinkedIn (NYSE:LNKD) hosted the in-person, all-day event at their San Francisco offices and facilitated the testing. Also participating were representatives from Cloudmark, Comcast (NASDAQ:CMCSA),, the Trusted Domain Project, and Message Systems/SparkPost.

“We set an aggressive target for testing when we announced the ARC protocol in October. AOL and Google did an outstanding job developing implementations and preparing test systems in time for this event,” said Steven M. Jones, executive director of ARC addresses a small but important class of messages, like mailing lists and forwarding services, that are impacted when a sending domain has a strong DMARC policy. Jones added, “I think ARC will allow more consumer mailbox providers and other domain operators to join AOL and Yahoo (NASDAQ:YHOO) in adopting such policies in order to better protect their users and their users’ correspondents from fraudulent messages.”

More implementations of ARC are under development, including an open source package that could be used to add ARC capabilities to existing email services. Additional interoperability testing events will be held between now and mid-year. For more information please visit the ARC protocol website at




ARC Interoperability Testing Day: February 19th

The interoperability testing event mentioned when ARC was announced in October (see this press release) has been scheduled for Friday, February 19th, 2016 in San Francisco. Parties implementing the ARC protocol in their product or service by that date should consider participating in the event. Those parties should join the arc-discuss mailing list if they aren’t already on it, and may express interest in the interoperability event there or via this contact form.

What qualifies as “implementing ARC” for this event?

  • Writing code (library, milter, MTA) that implements ARC functionality (signing, verifying, etc)
  • Building a free/commercial product that includes ARC functionality, whether you wrote the ARC code or not
  • Deploying ARC functionality in an intermediary (e.g. MLM) or receiver (e.g. mailbox provider) by the time of this event

If you have further questions, please bring them to the arc-discuss mailing list.